When collecting global navigation satellite systems (GNSS) data, it is often useful to know the accuracy of the determined position. Some existing Global Positioning System (GPS) receivers output an estimate of the accuracy of the position calculated at each epoch. This estimate is known as a real-time accuracy estimate.
Many users perform post-processed differential correction to improve the accuracy of the GPS positions. The real-time accuracy estimate is not a good indication of the accuracy that will be achieved later after post-processing. For example, a receiver may be calculating autonomous positions or may be applying differential corrections to code solutions whereas the processor may be calculating more accurate carrier-phase solutions.